Patrick ... I think your saw may well have a scoring saw on it!
Note the hole above the adjustment wheel.
That's where the rod and knob for the scoring height adjustment goes.

You're possibly missing some parts, but if that price on there is correct, no worries!
You do have a miter gauge too .... lucky @$##!

Nice score!!

And as to that rigger, that may be the best $300 you'll spend since you bought the saw!

I foresee many hours of your time being consumed by perusing over Patrick Walsh's excellent restoration of his T75.....